1. Field of the Invention
The present invention relates to a determination of whether a power supply apparatus such as a battery pack and an AC adapter has a satisfactory level of safety. More particularly, the present invention relates to an electrical apparatus capable of determining whether a power supply apparatus satisfies a predetermined safety specification.
2. Description of the Background Art
A consumable product, such as a battery pack (hereinafter, referred to as a “BP”) of a lithium ion battery, which is attached to an electrical apparatus, needs to satisfy a predetermined specification in order to assure a safety. When a BP which does not satisfy the predetermined specification (e.g., a non-licensed product) is used, a fluid leakage or heat generation of the BP may occur. Note that a licensed product is defined as a product which is developed and manufactured by a manufacturer of the electrical apparatus for which the BP is used, or a manufacturer licensed by the manufacturer, and which has the safety confirmed by the manufacturers. Any product which does not satisfy a definition mentioned above is defined as a non-licensed product. Therefore, it is extremely impotent to check whether or not a BP attached to an electrical apparatus satisfies a specification regarding the safety (hereinafter, referred to as a “safety specification”). As a method of checking whether the BP satisfies the safety specification, the following methods are used. Note that the safety specification defined in the present invention includes various specifications such as an official specification, a specification provided by a company, and a product specification adopted for each product. (In general, the product specification adopted for each product is not a standardized specification.)
Firstly, a method, of mounting a BP to a main body of an electrical apparatus only when a shape of a BP container of the electrical apparatus structurally coincides with a shape of the BP, is used. There is also a method of previously writing a predetermined ID code into an EEPROM of a BP. In this method, an electrical apparatus reads the ID code, and if the read ID code has desired contents, it is determined that the BP satisfies the safety specification.
Furthermore, a method, of mounting an exclusive encryption IC to an electrical apparatus and a BP, is also used. In this method, the exclusive IC has a security code written therein, and whether the BP satisfies the safety specification is detected by using a method such as a CHAP (Challenge Handshake Authentication Protocol) between the electrical apparatus and the BP.
Still furthermore, a method, of mounting a resistance or a thermistor to a BP, is also used. In this case, a predetermined voltage is applied from an electrical apparatus to the BP, and a resistance value of the BP is read based on a voltage division ratio. Or a predetermined constant current is applied from the electrical apparatus to the BP, and reads a voltage of the BP, thereby reading a resistance value of the BP. If the read resistance value is different from a predetermined value previously set as a normal value, it is determined that the BP does not satisfy the safety specification.
Still furthermore, a method of mounting, instead of the resistance or the thermistor, an element having a special characteristic (a characteristic changed over time) to a BP is also used (Japanese Laid-Open Patent Publication No. 2005-110210, for example). In this method, an electric power is supplied to the element having the special characteristic, and detects an electrical characteristic of the element, thereby determining whether or not the BP satisfies the safety specification.
However, the aforementioned methods have the following problems. Firstly, in the method of causing the shape of the BP container of the electrical apparatus to structurally coincide with the shape of the BP, even if the BP does not satisfy the safety specification, the BP may be mistakenly mounted to the electrical apparatus if the BP has a shape imitating that of the BP container. Furthermore, similarly to the aforementioned method, in the method of previously writing the predetermined ID code in the EEPROM of the BP, even if the BP does not satisfy the safety specification, the BP may be mistakenly mounted to the electrical apparatus if an EEROM of the BP has contents copied from that of a BP satisfying the safety specification. Still furthermore, in the method of mounting the exclusive encryption IC to the electrical apparatus and the BP, the exclusive IC needs to be separately provided, thereby generating an extra cost. In the method of using the resistance or the thermistor, the BP may be mistakenly determined to satisfy the safety specification if the resistance or the thermistor is copied, and the BP includes such a copied component. Still furthermore, in the method disclosed in Japanese Laid-Open Patent Publication No. 2005-110210, the element having the special characteristic needs to be separately provided, thereby generating an extra cost.